Back in the old days, we sent our secret stuff by teletype to Langley.
We had a one-time roll of random(?) stuff on one tape, and our data on another. We exclusiveored the two tapes together and sent the message.
Back at headquarters they had the same tape as we did.
When they received our encrypted data, they exclusiveored their tape against it, and the clear data then reappeared.
I know that we destroyed our encryption tape, and assume they did the same at their end.
With tape it may be pretty easy to destroy the used portion while retaining the rest. Until fairly recently, the only really lightweight way to transport a lot of data would have been on something like a CD or DVD, and unrecoverably-destroying part of the information on one of those without harming the rest would be difficult. With most "packaged" solid state media the same problems apply, but with a "raw" NAND-flash chip partial data destruction is no problem.